Refractory structure for a rotary kiln



Jan. 4, 1966 s. H. VAUGHAN, JR 3,

REFRACTORY STRUCTURE FOR A ROTARY KILN 4 Sheets-Sheet 1 Filed June 24, 1964 INVENTOR. SAM U EL H.VAUGHAN,J R.

ATTORNEY Jan. 4, 1966 s, H. VAUGHAN, JR 3,227,430

REFRACTORY STRUCTURE FOR A ROTARY KILN Filed June 24, 1964 4 Sheets-Sheet 2 INVENTOIE. SAMUEL H. VAUGHAN, JR.

ATTORNEY Jan. 4, 1966 s. H. VAUGHAN, JR

REFRACTORY STRUCTURE FOR A ROTARY KILN 4 Sheets-Sheet 5 Filed June 24, 1964 INVENTOR. SAMUEL H. VAUGHANJR.

ATTORN EY YIIEII 7 Jan. 4, 1966 H. VAUGHAN, JR 3,227,430

REFRACTORY STRUCTURE FOR A ROTARY KILN Filed June 24, 1964 4 Sheets-Sheet 4 INVENTOR.

FIE-S BY ATTORNEY SAMUEL H. VAUGHAN,JR.

3,227,430 REFRACTORY STRUCTURE FOR A ROTARY KILN Samuel Vaughan, Jr., Mexico, Mo., assign'or to Kaiser Aluminum & Chemical Corporation, Oakland, Calif., a corporation of Delaware Filed June 24, 1964, Ser. No. 377,543 8 Claims. (Cl. 263-33) This invention relates to rotary kilns and particularly to internal structures for such kilns.

In a rotary kiln, generally comprising a refractory lined, elongated metalcylinder or tube with its longitudinal axis inclined at a small angle to the horizontal, material to be treated is fed to the kiln at its upper end and a burner or other source of heat is directed into the kiln at its lower end. As the kiln is rotated about its longitudinal axis, the material to be treated flows by gravity down the length of the kiln, passing out the hot or lower end of the kiln. During its passage through the kiln, the material undergoes physical or chemical changes or both.

One of the important processes taking place in a rotary kiln is the heating of material in the upper or cooler end of the kiln by the hot gases passing up the kiln from the burner. It is desirable to extract as much heat from the hot gases as possible since any heat not extracted is carried out of the kiln by the outgoing gases and may be wasted.

Various means have been suggested to increase the efficiency of heat transfer between the hot gases and the material in the kiln. For example, it is known to insert chains in the cold or upper end of the kiln. It is also known to insert lifters in the lining of the kiln to raise the material being treated as the kiln rotates and allow it to drop back through the hot gases. It has also been suggested to insert longitudinal walls .or dividers into the cooler end of the kiln to divide the kiln into two or three or more parallel sections or segments or passages, thus increasing the amount of contact between the material being treated and the hot gases.

Such walls or dividers as heretofore constructed suffer from several disadvantages. For one thing, they have usually been made from preformed refractory shapes and the problem of building straight walls within a circular kiln has necessitated the use of many specially shaped pieces assembled in precisely the correct relationship. Not only is it expensive to form the particular special shapes required for such a structure, but it is also difiicult and time consuming for workmen assembling such a structure to place each special shape in its correct position in the structure. Another disadvantage of prior art divider or -wall structures is that they are relatively rigid and have a tendency to crack and break under the stresses induced by flexure of the kiln as it rotates. As will be understood by those skilled in the art, the shellof arotary kiln, ideally circular, actually assumes an oval shape under its own weight and the weight of its lining, the long axis of the oval being horizontal and the short axis vertical. As the kiln rotates, the long and short axes remain fixed relative to the earth but move relative to a given point in the kiln, thus causing flexing or bending of different parts of the kiln.

It has now been found that it is possible, by the structure of this invention, to build an internal heat exchanger structure in a rotary kiln which comprises refractoryretaining means or reinforcement made of metal and a monolithic refractory placed by gunning, casting, or the like. The structure according to this invention is relatively easy and simple to assemble and install, provides mobility or flexibility in the structure to accommodate the flexing of the kiln as it rotates, and also permits the passing of air or other cooling fluid through passages within the United States Patent 3,227,430 Patented Jan. 4, 1966 internal structure itself, thus cooling the structure and tending to prolong its life.

The invention will be best understood from the following description taken in conjunction with the drawings, in which:

FIGURE 1 is a perspective view of a rotary kiln, partly broken away, showing the general arrangement of the heat exchanger structure of this invention;

FIGURE 2 is a cross section view of a rotary kiln according to the invention taken perpendicular to the longitudinal axisof the kiln and showing the metal framework of the internal heat exchanger structure;

FIGURE 3 is a cross sectional view similar to FIGURE 2 but slightly displaced along the axis of the kiln and showing the refractory material in place;

FIGURE 4 is an elevational view, partially broken away, along the line 4-4 of FIGURE 2;

FIGURE 5 is a longitudinal cross-section view similar to FIGURE 4 but showing an embodiment of the frame structure of the present invention wherein interior plates are omitted;

FIGURE 6 is across sectional view of one embodiment of a support means according to this invention;

FIGURE 7 is a cross sectional view of another embodiment of a support means according to this invention;

FIGURE 8 .is a perspective view similar to FIGURE 1 but showing an alternative embodiment; and

FIGURE 9 is a sectional view similar to FIGURE 3 but showing the embodiment of FIGURE 8.

In erecting the structure of the present invention within a rotary kiln 11 having an external metal shell 12 and longitudinal axis 13, there are attached to the inside of the metal shell 12 a plurality of support means such as projections or studs or lugs 15. The lugs 15 are of metal, prefenably ferrous metal, and are attached to the metal shell 12 by welding or threads or other suitable means as desired. The lugs or projections 15 are spaced from each other and are disposed in rows running generally longitudinally of the kiln, the number of rows depending upon the number of radial sections into which the kiln is to be divided. Thus, for example, in the drawings a division of the kiln into three sections is shown. In this embodiment, then, there are three rows of lugs 15 afiixed to the interior surface 14 of shell 12 for the distance along the kiln over which it is desired to construct the heat exchanger structure.

It will be understood that the heat exchanger structure according to this invention is spaced from the upper end of the kiln and continues for any desired distance along the length of the kiln. In a preferred embodiment, such structure terminates less than half-way down the kiln from the upper end or, in other words, extends from adjacent the cold end to not over about one-half the length of the kiln. It will be understood that the interior of the kiln can, alternatively, be divided into two or into four or more radially disposed sections within such structures. Generally, however, it is preferred to divide the kiln into at least three such sections therein. In a preferred em bodiment, each row of lugs 15 along the inside of the metal shell 12 is disposed parallel to the longitudinal axis 13, and the rows then are also parallel to each other. However, the rows of lugs 15 can be disposed at an angle to the axis 13 when it is desired to make a spiral or twisted heat exchanger structure.

Mounted on each of the lugs 15 is a metal spoke 16 having its outer end disposed adjacent lug 15 and its inner enddisposed adjacent the longitudinal axis 13 of the kiln 11. Preferably, spoke 16 is slidably m-ountedon lug 15, as, for example, by making at least the end portion of the spoke hollow and of such an inside diameter that it will receive the end of the lug 15. For convenience in construction of the heat exchanger of this invention, spoke 16 can, after being placed over lug 15, be temporarily secured to the lug 15, as by tack-welds 17. While continuous welds can be made at the junction between spokes 16 and corresponding or associated lugs 15, it is preferred that only a temporary, breakable joint, for example tack weld 17, be made at this point so that the temporary joint will be broken under the stresses in the rotating kiln, thus effecting a mounting of spokes 16 on lugs such that spokes 16 are slidable in the direction of their length with respect to lugs 15. This slidable mounting gives a mobility or resilience to the entire structure which enables it to withstand strains due to fiexure during rotation of the kiln.

The inner end of each spoke 16 is attached to an arm 22 of a central connector 19 which can comprise, for example, as shown in the drawings, three tubular pieces of metal joined at the center, as by welding, to form a central connector having three outwardly extending arms 22. These arms are preferably spaced from each other at equal angles. For instance, in a three-section heat exchanger arms 22 are spaced 120 from each other. It is preferred that the spokes 16 be pivotally attached to arms 22 of central connector 19 whereby the outer end of an arm 22 is disposed within the hollow end of spoke 16 and is pivotally connected thereto by pin which passes through suitable, aligned apertures in 22 and in 16 and which is provided with suitable keys or cap nuts to retain it in position. The pivotal or pin joints between the spokes 16 and central connectors 19 add to the flexibility of the heat exchanger structure. Most preferably the pins 20 are placed so that their axes are substantially parallel to the longitudinal axis 13 of the kiln 11.

The element disposed between a support means or projection 15 and central connector 19 is suitably a rod, which is termed herein a spoke. This element in one embodiment is hollow, but in another embodiment, shown in FIGURE 6, is solid and is provided at each end with hollow portions, one of which fits over the end of projection or lug 15 and the other or opposite end portion over the end of arm 22 of central connector 19. In still another embodiment, shown in FIGURE 7, the support means 15 is a tubular piece of metal and the spoke 16 terminates in a tongue of reduced cross-section with respect to the cross-section of the main body of the spoke. This tongue is disposed within tubular support means 15 and is movable with respect thereto as the kiln shell 12 flexes with the rotation of the kiln.

For ease and economy of construction and for uniform operation of the kiln, it is preferred that central connectors 19 lie substantially on the longitudinal axis 13 of the kiln 11 and that, consequently, spokes 16 be all of substantially the same length and all lie or extend substantially perpendicular to the metal shell 12 of kiln 11 and to its axis 13. Also for ease of construction, it is preferred that corresponding lugs in the different rows, i.e., the first, second, etc. lugs, be placed on the same circumference, or the same periphery of the same circular cross-section, of the rotary kiln 11. That is to say, by the word circumference is meant the line of intersection between the shell of the kiln and a plane perpendicular to the longitudinal axis 13 of the kiln 11. Also, it is generally desirable that the rows of lugs be equally spaced about the circumference of the kiln. When corresponding lugs 15 in each row are placed on the same circumference of the kiln 11, the spokes 16 attached to the lugs 15 on one circumference will all lie in the same plane and be aligned with the mating arms 22 of the central connector 19. Thus, a single central connector 19 can be used to join all three spokes. While the central connector 19 joining these spokes can be joined, if desired, to the central connector 19 connecting the next adjacent set of spokes 16, it is preferred, for convenience in construction, that the central connectors 19 not be connected with each other.

It will be understood that the corresponding lugs 15 in different rows can lie on different circumferences of the kiln 11. In this event, spokes 16 will not meet at the same point along the longitudinal axis 13 and the central connector 19 can be a continuous means, e.g. a rod or pipe, with projections or arms 22 extending at appropriate points. However, it will generally be found that such a construction is less convenient to assemble and more expensive than the above-described central connector 19.

Between spokes 16 attached to adjacent lugs 15 in a given row are preferably placed plates 21. These plates extend from adjacent inner surface 14 of metal shell 12 of the kiln 11 to adjacent the longitudinal axis 13 of kiln 11, and from adjacent one spoke 16 to closely adjacent the neighboring spoke 16. They are attached to each spoke 16, for example by fingers 23 attached to spoke 16 and to plate 21, as by welding or bolting.

It will be seen that the spokes 16 attached to the lugs 15 in a row form a corresponding row of spokes. To the outer side of each spoke 16 in such a row is attached, for example by welding, a layer of apertured metal sheet such as metal mesh 24. The mesh shown, as an example only, in the drawings has openings of hexagonal configuration. This mesh is placed on each side of each row of spokes 16, and can extend from end to end of such spoke. However, it is preferred that the mesh 24 extend in a continuous curve along the sides of a row of spokes 16, over and past the central connector 19, and along the facing sides of an adjacent row of spokes 16. It is further preferred that the metal mesh 24 extend in a continuous curve over and past the outer ends of the spokes 16 in each row and continue in spaced relationship with the metal shell 12 of the kiln 11. For example, the mesh is spaced from the shell 12 by means of T-bolts or anchors 25 attached to the interior of the shell 12 and spaced from each other longitudinally and transversely. Thus, it will be seen that, in the most preferred embodiment, each radial section or passage into which the rotary kiln 11 is divided by the heat exhanger structure of this invention is continuously lined with metal mesh 24 attached to spokes 16 and anchors 25, forming a smooth, continuous lining for each section. It will be seen that the above described metal structure divides the kiln into three adjacent radial sections and forms a reinforcing structure for receiving refractory material.

After the metal structure has been erected within the kiln, the space between the metal mesh 24 and the kiln shell 12 and between the two layers of metal mesh 24 attached to each side of the rows of spokes 16 is filled with monolithic refractory material, for example by gunning or casting or ramming the refractory material, preferably a plastic refractory, into the spaces. The spaces will be filled with refractory material up to the outer or exposed surface of the metal mesh 24. The term outer surface of the mesh is intended to mean the surface facing the enclosed or central space of the radial section. In other words, the monolithic refractory surface is flush with the outer surface of the metal mesh 24. It will be understood that this monolithic refractory material, for example a fireclay gunning mix, is preferably of a type which sets to a hard coherent structure at room temperature and which is of such a composition that it remains hard and coherent at the operating temperatures of the rotary kiln 11, such monolithic refractory materials being well known in the art.

It will be seen that a special advantage of plates 21 is to retain the monolithic refractory material during its placement, for example by gunning. Thus, if plates 21 were not present, there would be a tendency for the monolithic refractory, when it is gunned, to pass through both thicknesses of metal mesh 24 and be wasted. In an alternative embodiment, however, the metal mesh can be used without lining plates such as plates 21. In this case a shield, for example, can be placed at one face of the double mesh wall and refractory gunned or cast into the space between the mesh sheets from the opposite face of the mesh.

It will be understood that the ends 28 and 28' of the heat exchanger structure within the rotary kiln 11 can be finished with metal mesh 24 attached to the metal shell 12 of the kiln 11 and to the end surface of the spokes 16 at the end of each row of spokes, the monolithic refractory 27 being brought out flush with the surface of this metal mesh 24 at the ends 28 and 28', whereby the mesh is embedded in the refractory.

Generally, for ease of construction, the lugs 15 in each row, and correspondingly the spokes 16 in each row, will be spaced from each other along the row at equal intervals, but in another mode of carrying out this invention the lugs and correspondingly the spokes are spaced from each other at irregular or nonequidistant intervals, if desired.

In one embodiment of the invention, shown in FIG- URE 2, the structure is such that air or other cooling fluid can pass from outside the metal shell 12 of the kiln 11 through the metal framework of the heat exchanger structure. Circulation of air or other cooling fluid is possible because the metal shell 12 of the kiln 11 has holes 29 placed so as to register with the openings of lugs 15, which are tubularelements. Likewise each spoke 16 is a hollow pipe and the central connector 19 is made of three joined, hollow arms 22 opening into or registering with each other at the center of this element. Thus, the structure provides a continuous passage from hole or aperture 29 through hollow lug 15', hollow spoke 16, and hollow arms 22 of central connector 19 through which cooling air or other fluid may be passed, either by natural convection or by artificially created pressure, on through arm 22", spoke 16" and tubular support element 15" and out through aperture 29" in shell 12.

In the alternative embodiment shown in FIGURES 8 and 9, ports or holes or openings 26 are placed in the dividing walls of the heat exchanger structure. The elfect of these holes is to impart additional motion to the material travelling. through the kiln and increase the heat exchange between the material and the hot gases. This structure allows the product being treated to not only travel down the kiln longitudinally, but also be transferred or exchanged between compartments on its journey down the kiln. This additional motion imparted to the product or material being treated eifects a slowing down of the material to get better heat exchange.

It will be understood that the metal parts of the heat exchanger structure can be made of any suitable metal, for example steel. For the load bearing parts of the structure, lugs 15, spokes 16, and central connectors 19, 25% chrome steel is particularly suited to the elevated temperatures encountered in a rotary kiln. While circular spokes 16 are shown in the drawings, it will be understood that square, rectangular, or other cross-sectional forms can be used. While preferred embodiments of the structure have been shown and described, it will be understood that other forms of the invention are possible within the scope of the appended claims.

Having described the invention,

What is claimed is: r

1. In a rotary kiln having a metal shell longitudinally inclined to the horizontal and an upper end and a lower end, a heat exchange structure disposed within said shell and comprising a metal reinforcing frame work comprising a plurality of generally longitudinal rows of outer support means afiixed to the interior surface of said shell, a central support means disposed at the axis of said kiln, a plurality of rows of connector means disposed between said rows of outer support means and said central support means, each of said connector means being connected with one member of said row of outer support means and with said central support means, apertured metal sheet disposed over said outer support means, said central support means and said connector means and de- 6 fining a plurality of radially disposed interior sections of said kiln; and refractory material disposed within said apertured metal sheets and embedding substantially all of said support means.

2. A heat exchange structure according to claim 1 wherein said outer support means are lugs, said connector means are spokes slidably connected to said lugs, and said refractory material is a plastic refractory.

3. A heat exchange structure according to claim 2 wherein said structure includes dividing walls having ports disposed therein permitting access from one radial section to another of said sections.

,4. In a rotary kiln h avng a metal shell and a longitudinal axis, an internal structure comprising: studs attached to the interior of said shell, said studs being located in rows; spokes having inner and outer ends; central connectors, the outer ends of said spokes being mounted on said studs and the inner ends of said spokes being attached to said central connectors, said spokes forming rows corresponding to the rows of studs; metal mesh attached to the spokes in each row; and monolithic refractory filling the space between the surfaces of the mesh and the spokes to which the mesh is attached.

5. In a rotary kiln having a metal shell and a longitudinal axis, an internal structure comprising: studs attached to the interior of said shell, said studs being located in rows said rows being substantially equally spaced about the circumference of the kiln shell; spokes,

all .of substantially equal length, having inner and outer ends; central connectors, the outer ends of said spokes being mounted on said studs so that said spokes are slid.- .able in the direction of their length with rcspect to said studs, said spokes lying radially with respect to the kiln axis, the inner ends of said spokes being pivotally attached to said central connectors, said spokes forming rows corresponding to the rows of studs; plates disposed between and attached to the spokes mounted on adjacent studs in a row; metal mesh attached to both sides of the spokes in each row; and monolithic refractory filling the space between the surfaces of the mesh and the spokes to which the mesh is attached.

6. In a rotary kiln having a metal shell and a longitudinal axis, an internal structure comprising: studs attached to the interior of said shell, said studs being located in rows running substantially longitudinally of said kiln, said rows being substantially equally spaced about the circumference of the kiln shell, corresponding studs in each row being located on substantially the same circumference of the kiln shell; spokes, all of substantially equal length, having inner and outer ends; central connectors, the outer ends of said spokes being mounted on said studs, said spokes lying radially with respect to the kiln axis, the inner ends of said spokes attached to corresponding studs on the same circumference of the kiln shell being attached to a common connector, said spokes forming rows corresponding to the rows of studs; metal plates disposed between and attached to the spokes mounted on adjacent studs in a row; metal mesh attached to both sides of the spokes in each row, said mesh extending from the vicinity of the outer ends of the spokes in each row to the vicinity of the inner ends of said spokes in each row, past the central connectors and to the vicinity of the outer ends of the spokes in an adjacent row said mesh also extending past the outer ends of the spokes into spaced relationship with the kiln shell, the mesh on facing sides of adjacent rows of spokes and on the intervening kiln shell forming a continuance structure; and monolithic refractory filling the space beween the surfaces of the mesh and the spokes to which the mesh is attached and the space between the mesh and the kiln shell.

7. In a rotary kiln having a metal shell and a longitudinal axis, an internal structure comprising: studs attached to the interior of said shell, said studs being located in rows running substantially longitudinally of said kiln, said rows being substantially equally spaced about the circumference of the kiln shell; spokes, all of substantially equal length, having inner and outer ends; central connectors, the outer ends of said spokes being mounted on said studs so that said spokes are slidable in the direction of their length with respect to said studs, said spokes lying substantially radially with respect to the kiln axis, the inner ends of said spokes being pivotally attached to a central connector, the axis of said pivotal attachment being substantially parallel to the kiln axis, said spokes forming rows corresponding to the rows of studs; metal plates disposed between and attached to the spokes mounted on adjacent studs in a row; rnetal mesh attached to both sides of the spokes in each row, said mesh extending from the vicinity of the outer ends of the spokes in each row to the vicinity of the inner ends of said spokes in each row, past the central connectors and to the vicinity of the outer ends of the spokes in an adjacent row, said mesh also extending past the outer ends of the spokes into relatively closely spaced relationship with the kiln shell, the mesh on facing sides of adjacent rows of spokes and on the intervening kiln shell forming a continuous structure; and monolithic refractory filling the space between the surfaces of the mesh and the spokes to which the mesh is attached and the space between the mesh and the kiln shell.

8. In a rotary kiln having a metal shell and a longitudinal axis, an internal structure comprising: studs attached to the interior of said shell, said studs being located in rows said rows being substantially equally spaced about the circumference of the kiln shell and corresponding studs in each row being located on substantially the same circumference of the kiln shell; spokes, all of substantially equal length, having inner and outer ends;

central connectors, the outer ends of said spokes being mounted on said studs, said spokes lying substantially radially with respect to the kiln axis, the inner ends of said spokes attached to corresponding studs on the same circumference of the kiln shell being attached to a common central connector, said spokes forming rows corresponding to the rows of studs; metal mesh attached to the spokes in each row, said mesh extending from the vicinity of the outer ends of the spokes in each row to the vicinity of the inner ends of said spokes in each row, past the central connectors and to the vicinity of the outer ends of the spokes in an adjacent row, said mesh also extending past the outer ends of the spokes into spaced relationship with the kiln shell, the mesh on facing sides of adjacent rows of spokes and on the intervening kiln shell forming a continuous structure; and monolithic refractory filling the space between the surfaces of the mesh and the spokes to which the mesh is attached and the space between the mesh and the kiln shell; said spokes, said studs, and said central connectors being hollow and interconnected, and the kiln shell having holes at the points of attachment of the studs whereby cooling fluid can pass from outside the kiln in toward the axis of the kiln through certain of said spokes and out from the axis of said kiln through others of said spokes.

References Cited by the Examiner UNITED STATES PATENTS 631,298 8/1899 Grill 26333 1,797,831 3/1931 Luther 263-32 3,175,815 3/1930 Wicken et al. 26332 WILLIAM F. ODEA, Acting Primary Examiner. 

1. IN A ROTARY KILN HAVING A METAL SHELL LONGITUDINALLY INCLINED TO THE HORIZONTAL AND AN UPPER END AND A LOWER END, A HEAT EXCHANGE STRUCTURE DISPOSED WITHIN SAID SHELL AND COMPRISING A METAL REINFORCING FRAME WORK COMPRISING A PLURALITY OF GENERALLY LONGITUDINAL ROWS OF OUTER SUPPORT MEANS AFFIXED TO THE INTERIOR SURFACE OF SAID SHELL, A CENTRAL SUPPORT MEANS DISPOSED AT THE AXIS OF SAID KILN, A PLURALITY OF ROWS OF CONNECTOR MEANS DISPOSED BETWEEN SAID ROWS OF OUTER SUPPORT MEANS AND SAID CENTRAL SUPPORT MEANS, EACH OF SAID CONNECTOR MEANS BEING CONNECTED WITH ONE MEMBER OF SAID ROW OF OUTER SUPPORT MEANS AND WITH SAID CENTRAL SUPPORT MEANS, APERTURED METAL SHEET DISPOSED OVER SAID OUTER SUPPORT MEANS, SAID CENTRAL SUPPORT MEANS AND SAID CONNECTOR MEANS AND DEFINING A PLURALITY OF RADIALLY DISPOSED INTERIOR SECTIONS OF SAID KILN; AND REFRACTORY MATERIAL DISPOSED WITHIN SAID APERTURED METAL SHEETS AND EMBEDDING SUBSTANTIALLY ALL OF SAID SUPPORT MEANS. 